1. Field of the Invention
This invention relates to capacitive-to-digital converters, and more particularly to capacitive-to-digital converters to sense a parameter using a bridge circuit.
2. Description of the Related Art
Capacitance-to-digital conversion plays an important role in many sensor applications such as measurement of pressure and humidity. In these sensing applications, key performance metrics include measurement range, resolution (i.e. rms noise of each measurement sample), accuracy, conversion time, area, and power consumption.
Due to the small size of capacitances that must be detected, analog amplifiers typically form a critical building block of capacitance-to-digital converters. These amplifiers often pose performance limitations due to their finite DC gain, nonlinear gain characteristic, and limited output swing. The finite DC gain and nonlinear gain characteristic of the amplifier can lead to nonlinearity in the capacitance-to-digital measurement characteristic, which degrades its accuracy performance. The limited output swing of the amplifier can lead to the need for a large area for the capacitance-to-digital converter in order to properly scale down voltage levels. Thus, improvements in capacitance-to-digital conversion are desirable.